I'm a student in electrical engineering in Belgium and I use a multiple feedback bandpass filter in one of my projects.
I tried to find out the transfer function of this filter and this is what I found:
$$ \frac{V_o}{V_i}=-\left( j\omega C+ \frac{2}{R_2}+\frac{R_1+R_3}{R_1R_2R_3}\cdot\frac{1}{j\omega C} \right) ^{-1} $$
With this expression I made a Bode diagram:
Is that normal that the frequencies other than 1kHz are still amplified (not as much but still) ? Is my transfer function right ?
Thanks !